Numerical study on steam-added mild combustion

Abstract

SUMMARYNumerical study on flame structure and NO emission is conducted covering a wide range of atmospheric temperature, high temperature, and mild combustion regimes in H 2 -Air laminar flames diluted with steam. Special concern is focused on the difference of flame structure and NO emission behaviour between hightemperature combustion and mild combustion modes. The important role of chemical effects of added steam in flame structure and NO emission behaviour is also discussed. It is seen that there exists an oxidizer-side temperature limit which the combustion mode changes from high temperature combustion to mild combustion. In high temperature combustion modes the OH production via the reaction step, (-R23) is suppressed while in mild combustion modes is enhanced by the increase of oxidizer-side temperature. It is also found that chemical effects of added steam are influenced by the competition between both the reaction steps, (R21) and (-R23).NO emission index increases with increasing oxidizer-side temperature and decreases with mole fraction of added steam. The remarkably produced OH due to chemical effects of added steam does not contribute to the increase of NO but plays a role of holdback on NO in thermal mechanism. It is also seen that in both the high temperature combustion and mild combustion modes NO emission indicates a consistently similar tendency, and is consequently recognized that in the whole ranges steam addition suppresses NO emission.

Numerical study of further NO x emission reduction for coal MILD combustion by combining fuel‐rich/lean technology

“…Since previous studies have already shown that the high heating rate is one of the main reasons for high volatile release rate, [52][53][54] it is deduced that the heating rate of the outer stream is higher than that of the inner stream. Equations (12) and (14) indicate a positive correlation between the concentration of NO and the reduction rate of NO by reacting with HCN and NH 3 . The IFRF furnace characterizes the strong recirculation of flue gas.…”

“…[2][3][4][5][6][7][8][9][10][11][12][13] The essence of this technology for coal combustion is to achieve strong recirculation of the injected streams so that the coal particles are heated and combusted in a highly substoichiometric condition. [2][3][4][5][6][7][8][9][10][11][12][13] The essence of this technology for coal combustion is to achieve strong recirculation of the injected streams so that the coal particles are heated and combusted in a highly substoichiometric condition.…”

“…Due to the potential of significant reduction of NO x emission, moderate or intense low-oxygen dilution (MILD) combustion has become a hot topic within the combustion committee worldwide and has been studied intensively. [2][3][4][5][6][7][8][9][10][11][12][13] The essence of this technology for coal combustion is to achieve strong recirculation of the injected streams so that the coal particles are heated and combusted in a highly substoichiometric condition. 14 As a result, the peak temperature is reduced, and thermal-NO formation is mitigated.…”

Numerical investigation on ignition intensification of n‐butane with tert‐butyl hydroperoxide (TBHP) addition

“…In this paper, the promoting effects of TBHP addition under different initial temperatures, pressures, and equivalence ratios were investigated by CHEMKIN‐PRO software . Furthermore, the acting mechanism of TBHP addition was studied in detail using the mole fraction and rate of production and consumption (ROP) analysis, sensitivity analysis, and reaction pathway analysis …”

A review of MILD combustion and open furnace design consideration

“…All the nozzles and exhausts were at the bottom of the furnace. This MILD combustion setup has produced data on various experiments, including fuel tests, flame tests, NO x tests, and heat exchanger tests (Christo and Dally, 2005;Colorado et al, 2009;Dally et al, 2002Dally et al, , 2004Dally et al, , 2010de Joannon et al 2009de Joannon et al , 2010Flamme, 2004;Li et al, 2011b;Lou et al, 2007;Maruta et al, 2000;Medwell et al, 2007Medwell et al, , 2008Mi et al, 2009;Mörtberg et al, 2006;Oryani et al, 2011;Park et al, 2004;Stankovic, 2006). MILD combustion technology is still not fully commercialized and well adopted in the furnace industry, thus it is very important to conduct substantial fundamental and applied research (Cavaliere et al, 2008;Danon, 2011;Li et al, 2011b;Parente et al, 2011aParente et al, , 2011b.…”